This is a particularly great suggestion. I like your idea here much more than I like any of the ones I proposed. I wish itch.io discussion boards were busier and more important places; I want your suggestion to be a seed we plant.
Your specification of projectile hang-time determining whether it gets disintegrated, and your proposition of it waiting until the latter half, each are particularly earning my obsessive reverence. They both give Mrs. Slitherss a way to defend against projectiles while offering balance, *and* in a way that would be fun to play against and around.
Also, lore/character-development squealer I am, I love the idea of Mrs. Slitherss being portrayed right down to gameplay, as you yourself point out, being "a quick learner from experience". This would cement her status as a teacher; the best teacher is a great learner.